Liquid limestone in the acidity correction of a Dystric Cambisol for Brachiaria production in Humaitá , Amazonas

Conventional solid limestone most commonly used in agriculture generally has disadvantages in handling, in addition to a certain infeasibility for small producers when compared to the use of liquid limestone with high purity and reactivity. Therefore, a better understanding of the Research, Society and Development, v. 9, n. 8, e415985517, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i8.5517 3 dynamics of liquid limestone employed in soil acidity correction is important. Thus, this work proposes the use of liquid limestone to correct the acidity of a Dystric Cambisol in pasture cultivation in Humaitá, AM. An experiment was carried out in a greenhouse, where plastic pots were prepared for sowing Brachiaria brizantha, in a randomized block design with five treatments and four replications (T1 = witness, T2 = 2.5 L, T3 = 5 L, T4 = 10 L and T5 with common limestone). After 90 days of planting, the shoot and root size of both fresh and dry mass of each treatment were evaluated, as well as the number of tillers. The tillering of B. brizantha was highly responsive to the addition of liquid and common limestone, so that the higher the dose, the greater the results. In contrast, the treatments for fresh and dry shoot and root biomass production did not differ significantly between themselves, explaining why the product is still not well accepted and used by dealers and farmers.

In order to minimize these problems, it has been proposed to use calcium carbonatebased fluid fertilizers to be sprayed into the soil to provide Ca2+ and possibly correct soil acidity. These products have high purity and reactivity (100%), as they consist of nanoparticles (0.5 -0.8 microns), and have a ECCE of 140. Because they are fluid, they improve the dispersion of particles when applied to the soil and prevent dust emissions, reducing losses. Another important factor is the ease of transportation of this product, which occupies less volume compared to limestone, making it possible for small and large farmers to use it, even in regions with difficulties in purchasing, as for example in Amazonian regions, where transportation is a limiting factor.
The sources and preparation processes of these liquid fertilizers allow greater flexibility compared to solids and, according to Bittencourt and Beauclair (1992), there is also easier handling, uniformity of soil application, elimination of storage problems and lower operating costs.
Therefore, it is important to understand the dynamics of calcium carbonate-based fluid fertilizers to correct soil acidity. Thus, this work aimed to use liquid limestone to correct the acidity of a Dystric Cambisol in the production of brachiaria grass in Humaitá, AM.

Material and Methods
The experiment was carried out in a greenhouse of the Institute of Education, Agriculture and Environment (IEAA-UFAM), in the municipality of Humaitá-AM. It was collected 5.0 dm -3 of soil, with bulk density of 1.2 mg.dm -3 , and transferred to plastic vases with capacity of 6 dm -3 . The soil collected was classified as a Cambissolo Háplico Alitico Plintico (Campos, 2009) [Dystric Cambisol (Alumic, Clayic)]. The soil was sampled deformed under a 0.0-0.20 m layer, then processed and obtained the fine-earth fraction for Research, Society and Development, v. 9, n. 8, e415985517, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i8.5517 6 texture determination and routine chemical analysis for fertilization and liming (Table 1), according to the methodology proposed by Claessen et al. (1997).  The experimental design was randomized blocks with five treatments and four replications. One treatment consisted of limestone application to increase base saturation to 50%, which is the most common management for soil acidity correction; the other treatments correspond to different doses of liquid fertilizer, which make up one ton of limestone. Thus, we have the following: T1 = Witness, T2 = 2.5 L, T3 = 5 L, T4 = 10 L and T5 with common limestone. The liquid fertilizer has in its chemical composition 22.5% Ca 2+ ; 16% Mg 2+ and 18% S, with 100% reactivity and ECCE 140. The common limestone used has in its chemical composition: ECCE 85.08%; 36.4% CaO; 14% MgO. The applied amount of common limestone was 1000 kg ha-1.
Sowing of Brachiaria brizantha cv. Marandú was carried out with ten seeds per vase and, after the establishment of the plants, thinning was done, leaving five seedlings per vase.
The following agronomic traits of Brachiaria were evaluated: number of tillers -established by counting the total number of tillers at the beginning of flowering, randomly sampled; aerial height and plant root size. Then, the dry mass of the aerial part and roots were determined after drying in an oven at 60 ° C until constant weight.
The data obtained in the experiment were subjected to analysis of variance and, when significant, the Tukey test at 5% was applied to compare the means by the computer application Assistat 7.6 (Silva and Azevedo, 2002).

Results and Discussion
The results show that treatment 3 (5 L ha-1 of liquid CaCO3) contributed the most to the development of fresh aerial part mass (FAPM) (Figure 1), with a production loss of Research, Society and Development, v. 9, n. 8, e415985517, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i8.5517 7 1786.12 kg ha -1 when treatment 4 (10 L ha -1 ) was applied, while the control presented the lowest biomass, with a value of 9658.33 kg ha -1 . This behavior was adjusted to a 90% correlation quadratic regression curve (r = 0.907; p < 0.05), showing that the best dose for B. brizantha FAPM increment is between 5 and 5.5 L ha-1 of liquid CaCO3. On the other hand, fresh root mass (FRM) showed an exponential growth (Figure 1), without much response until the 3rd treatment, but with a high increase when applied the 4th treatment (10 L ha-1), reaching about 6641.66 kg ha-1. Thus, there is a duality in FAPM and FRM between doses 5 and 10 L ha-1, thus being in an optimum state of use according to the commercial objectives of the crop and/or producer, since not always a system well developed root system is synonymous of aerial biomass yield.
As in the FAPM, the dry aerial part mass (DAPM) also presented a higher yield with treatment 3 (5574.00 Kg ha-1) (Figure 2), without much variation among the other treatments in relation to the control, which showed a dry biomass of 4208.33 kg ha-1. However, its correlation was lower than that of FAPM, with a value of 78%, due to the similarities between treatments 1, 2 and 4. Research, Society and Development, v. 9, n. 8, e415985517, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i8.5517 showed an exponential behavior similar to that of FRM, where the treatment with the highest dose also showed to be more efficient for the underground biomass increment. Regarding the number of tillers (Figure 3), treatments 3 and 4 were the most significant, in which treatment 3 showed a value of 2500 tillers per hectare and the 4th treatment a value of 3125 tillers per hectare. The lower tillering was confirmed in the control, which obtained a total of 1180.55 tillers per hectare, indicating that this species is highly responsive to the addition of CaCO3, but it also indicates that the higher the recommendation dose for a given area, the higher it will be workforce with cultural treatment, depending on the culture. According to the averages obtained, it was also observed that in addition to treatments 3 and 4, the 5th (common limestone) was also statistically higher than treatments 1 and 2 for the number of tillers (Table 2). This can be explained by increased soil pH, which is directly linked to increased phosphorus availability in the soil. Phosphorus is the most required nutrient in the first growth of forage grasses (Cantarutti et al., 1999), since its main role is associated with the establishment of the root system. The tillering is relevant, since the emission of leaves and tillers guarantees the perennial grass forage.
The results show that there was no significant effect of the application of liquid limestone for the production of dry and fresh mass of the aerial part and roots. The results corroborate with Alves (2015), who studying liquid limestone doses in soils cultivated with Marandu and Mombaça forages did not find any difference in the aerial dry matter production with the application of liquid limestone, even in increasing doses in both cultivars. The author also verified that for the dry matter of the root system, there was a reduction in production for both grasses in relation to the control treatment, without the application of liquid limestone.
Considering the use of common limestone, the DAPM showed the best result for treatment 5, which obtained an average value of 5797.44 Kg ha-1, but did not differ statistically from other treatments tested (Table 2).
These results were higher than those found by Ezequiel and Favoretto (2000), who obtained 35 days dry mass production of 1625 Kg ha-1 with colonião grass. Results found by Barros et al. (2002) showed an increase in dry mass production of 7600 Kg ha-1, being higher than those found in this study. Already Benett et al. (2008) working with nitrogen fertilization in Brachiaria brizantha observed an increase in dry mass production.
Studies of leaf dry mass production in forage grasses are important because the leaves are the organ of the plants preferentially consumed by animals, besides being the main source of nutrients for grazing ruminants (Rodrigues et al., 2008).
This also corroborates that crop yield depends on total biomass production and dry matter distribution between the productive and non-productive parts of the plant (Hole et al., 1983).
Regarding the variables fresh and dry matter of the root, no statistical difference was found between the different doses of limestone tested (Table 2).
It is possible to observe the same fact between the fresh matter values of the shoot as a function of the corrective doses, which did not differ statistically from each other. Therefore, the different corrective doses adopted in the experiment did not influence the determination of these agronomic parameters.

Conclusion and Suggestions
B. brizantha tillering was highly responsive to the addition of both liquid and common limestone, so that the higher the dose, the greater the results.
On the other hand, the parameters of fresh and dry biomass production from the aerial part and roots did not show differences at the 5% level between themselves, explaining why the product is still not well accepted and used by traders and farmers.
However, other factors such as economic viability and ease of local acquisition should be further investigated.